Backup Ubuntu 12.04 terminal which directories to backup ?

[ty74]

I am fascinated with the Linux terminal. I am currently learning how to backup files with tar, gzip, bzip2, zip, and rsync. I have not backed up my system yet and want to do it through the terminal,with the tar command (compressed with the -z option of course). I am stuck I just want to backup the changes I made to the system not the OS. The apps and programs I manually installed are my main concern. I was planning to 2 backup tars. One with the whole /home directory and the other with / and exclude /proc, /media, /system. I need opinions on what to exclude and what to include in my backup. I plan to run the live cd of ubuntu 12.04 and and the directories I need to restore it to my customized version. I would like to do it through the terminal if at all possible.